My first BP rifle was a Thompson Center Hawken in 45. It was accurate with Round ball as long as you didn't exceed 60 grs of 3fg and a tack driver with 80 grs of 3fg and a maxi ball. Great gun. Stolen out shipping when changing duty stations, but it cemented a love for BP hunting and shooting Black Powder guns.Get the TC 45 and find a 50 barrel to have.
Not even sure how many deer the latter combo load let me take home but it was plenty. Most dropped it place. A few ran but only around 60 yards or less. Shot placement and load construction trump's caliber in most cases.